Portable battery charger



FIG. 1 is a perspective view of a portable battery charger showing the new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is rear plan view thereof;

FIG. 4 is a right side elevation view thereof;

FIG. 5 is a left side elevation view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines in the figures represent portions of the article which form no part of the claimed design. 

CLAIM The ornamental design for a portable battery charger, as shown and described. 